As is known, the most commonly used guardrails are made of metal, and comprise a number of vertical supporting posts fixed successively into the ground along the edge of a road; and a number of longitudinal retaining members fixed horizontally and successively to the supporting posts to form a longitudinal retainer extending seamlessly along the edge of the road, at a given height off the ground.
Unfortunately, guardrails of the above type are carefully designed to stop and retain motor vehicles of normally over a ton in weight, while subjecting the occupants to deceleration below a regulation maximum limit, and so constitute potentially hazardous obstacles in the event of motorcyclists or cyclists falling and forcefully striking the supporting posts of the guardrail.
In fact, after falling, motorcyclists or cyclists invariably continue sliding along the tarmac until they hit one of the posts of the guardrail along the edge of the road, and most undergo serious injuries, which can be mortal even at relatively low impact speed, when the guardrail supporting posts have “sharp” edges.